We demonstrate the feasibility of fabricating thermo-optic plasmonic devices for variable optical attenuation and/or low-frequency (kHz) signal modulation. Results of finite-element simulations and experimental characterization of prototype devices indicate that a plasmonic device can reach specifications similar to or better than commercially available thermo-optic integrated optical components. Specifically, we have considered the insertion loss, power consumption, footprint, polarization-dependent loss, extinction ratio, and frequency response of the plasmonic devices, in addition to fabrication and material-related issues. The most serious fabrication challenge is to realize metallic nanowire waveguides with a sufficiently accurate cross-section to ensure low polarization-dependent loss at high extinction ratios.